Synthesis and characterization of large-sized monolayer MoS2 nanoflakes by sulfurization of exfoliated MoO3 powder

We demonstrate a novel approach based on sulfurization of MoO 3 powder pre-exfoliated on the SiO 2 /Si substrate to synthesize high crystalline quality and large-sized monolayer MoS 2 films uniformly covering the whole substrate. The surface morphology, thickness, crystalline quality, and luminescence mechanism of the MoS 2 films were characterized by the optical microscopy, Raman spectroscopy, and photoluminescence spectroscopy. The results reveal that MoS 2 films directly synthesized on the bare SiO 2 /Si substrate by our method have high surface coverage superior over those of one-step chemical vapor deposition (CVD) method and exhibit uniform monolayer with larger lateral length up to ∼120 µm compared to those of the traditional two-step CVD method. Our proposed growth strategy opens up new pathways for CVD synthesis of high crystalline quality and large-sized uniform monolayer MoS 2 films and can also be utilized for synthesizing other two-dimensional materials.